How can I open a web page from a different port on the same server in an iFrame on the dashboard?

Hi,

I have NR running on a Raspberry Pi. Dashboard and flows working nicely. I need to add a user interface that provides CRUD functionality on multiple, related tables (MySQL). My gut feeling (please enlighten me if wrong) that a UI like this is beyond NR thus I have begun to create a straight HTTP (express) web site that will do this part instead.

So, I have a nice dashboard in NR, and soon a nice web site for editing the more complex underlying data.

I'd like to add the web site to the dashboard as a "link" tab. However, because the site runs on the same server as NR, it is required to have a different port number. HTTP does not support links that are relative to the same server with a differing port, e.g. this doesn't ever work: 'http://:3000/index.html'. So, I need to use JavaScript to build the link, perhaps as:
'http://' + window.location.host + ':3000/'
However, it looks like the link field is just "dead" text with no dynamic capability.

My questions: how can I display my site as a tab in the dash? Can NR handle CRUD UI cleanly with half-a-dozen different tables?